The study of liquid membrane separation method can be traced back to the 1960 Scholamcle from the physiological point of view to study the use of aqueous solution containing hemoglobin to promote oxygen transport. Since Dr. Li Nianzhi obtained the patent for the first emulsion film in 1968, the technology has been used as a viable industrial separation method. Since the second half of the 1970s, international liquid film research has been very active. Industrial applied research carried out in the industrial wastewater treatment, hydrometallurgical and other fields.
Although the time for research on liquid membrane separation in China has not been long, great progress has been made. Since this technique is suitable for the separation and concentration of low-concentration substances, it has first received extensive attention and research in water treatment.
The liquid film is the third liquid phase film layer separating the two liquid phases I and II. The third liquid phase is insoluble in the liquid phases I and II. Stable liquid film types include diaphragm liquid membrane, impregnated liquid membrane and emulsified liquid membrane. The emulsified liquid film is composed of a W/O/W (W-water, O-oil) type or an O/W/O emulsion system.
Liquid film technology has the potential to be industrialized, both technically and economically. At present, two premise that industrial applications must be resolved at home and abroad:
1. Requires an ideal surfactant or liquid film enhancer to produce a more stable emulsion.
2. An effective demulsifier (coalter) is required to achieve oil phase reuse and concentrate recovery. This test is based on these two perspectives and has achieved satisfactory results.
First, the mechanism of liquid membrane separation CN-
2. Liquid membrane treatment of cyanide-containing wastewater
There are many methods for treating CN - containing wastewater, and various commonly used methods include acidification aeration-alkali absorption method and desorption method. Alkaline chlorination, electrolytic oxidation, pressurized hydrolysis, natural purification, biochemical and bio- iron . Each of these methods has its own advantages, but it has good treatment effect, simple equipment, low energy consumption, no secondary pollution and comprehensive utilization, and there are still some shortcomings:
The beneficiation process results Huaniushan lead zinc ore, some of wastewater containing cyanide required emissions. The water quality is shown in Table 1. In the experimental study, it was proposed to adopt a commonly used method-alkaline chlorination method to treat the water quality. This method has the advantages of simple operation and management, and low cost. However, the method is suitable CN - low content of waste water, CN - can not get the same yield. In order to recover the CN in the wastewater, we use the liquid membrane method combined with the coagulation sedimentation method to treat the water.
Table 1 contains CN - wastewater quality
Third, the processing process
The II method is superior to the I method. Because Pb 2+ Zn 2+ is removed first, the selectivity drop caused by liquid film swelling can be avoided. However, it was found in the experiment that the II method cannot remove Zn 2+ . This is because when the pH is equal to l0.00 and l1.00, the side reaction coefficients lgam(L) of the cyanide complex are 12.30 and 12.70, respectively, and Zn 2+ and CN - form [Zn(CN). 4 ] 2 - . Therefore, the process of treating wastewater can only use the I method.
Fourth, the conclusion
1. Separation of cyanide from cyanide-containing wastewater by liquid membrane separation techniques is technically feasible. Lan-ll3B is an ideal W/O type emulsifier.
2. The internal phase NaCN solution of the liquid film backwater is analyzed and determined, and the impurity content is in accordance with the requirement of NaCN for cyanide immersion gold production. Recycling the economic value of NaCN can offset some of the wastewater treatment costs and reduce costs. At the same time, the closed circuit of the wastewater can be basically realized. Reduce emissions to the environment. Its economic and environmental benefits are significant.
3. The stability of the prepared emulsion can meet the requirements of liquid membrane separation. In the case of high-voltage electric demulsification, the fork easily breaks the emulsion membrane and the separation rate is fast and can meet the cyanide removal requirement without causing secondary pollution.
4. The water method is used to treat the water quality of Table 1 and can meet the national â€œthree wastesâ€ emission standards.
5. The technical problem of the liquid film method - swelling, by improving the artistic conditions, to affect it to a lower level. But the blue beam is completely eliminated. Swelling causes the internal phase NaCN solution to be diluted and contaminated.
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